Dimethyl formiminium chloride chlorosulphate derivatives useful as intermediates for producing cephalosporins

ABSTRACT

This invention relates to reactive derivatives of 2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid and 1H-tetrazol-1-acetic acid of the following general formula I, ##STR1## wherein R 3  = ##STR2## as well as to use thereof in the manufacture of cephalosporin antibiotics such as cefotaxime, ceftriaxone and cefazolin.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to reactive derivatives of2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid and1H-tetrazol-1-acetic acid of the following general formula I, ##STR3##wherein R₃ = ##STR4## The present invention also relates to the processfor the production thereof as well as to the process for the use thereofin the manufacture of cephalosporin antibiotics such as cefotaxime,ceftriaxone and cefazolin.

Discussion of the Background

It is known in the art to synthesize different cephalosporinantibiotics, for instance compounds of formula II which generallycomprise of amidification of 7-position of appropriate cephalosporinnucleus with or without substitution at 3α-position, with the desiredaddenda. ##STR5## wherein R₁ =H, carboxylic protecting group;

R₂ =acetoxy, ##STR6## R₃ = ##STR7##

Usually, the synthesis by such known processes of various cephalosporinantibiotics comprises of acylation of 7-aminocephalosporanic acid(7-ACA) or 7-amino desacetoxycephalosporanic acid (7-ADCA) derivativeswith a reactive derivative such as an acid chloride, an acid anhydride,an activated ester, etc., of the addendum acid for instance of formulasIII and IV. ##STR8##

The above can be described schematically as follows: ##STR9## A numberof methods utilizing this concept have been reported for thefunctionalization of position 7 of the desired cephalosporin nucleus andthese are summarized below.

U.S. Pat. No. 4,152,432 describes acylation of 7-ACA with an acidchloride of formula V in which the amino group in the thiazole ring isprotected. The amino group is subsequently deprotected generally byhydrolysis or hydrogenolysis. ##STR10##

Because of the inherent inefficiency of amidification of the 7-aminogroup of cephalosporin nucleus and also of the steps involved inprotection and deprotection of the amino group of the thiazolyl ring,the overall yields are low and far from satisfactory. JP 52-102096, JP53-157596 and GB 2 025 933 utilize the same chemistry--i.e., formationof 2-(2-aminothiazol-4-yl)-2-oxyimino acetyl chloride either with PCl₃,PCl₅, SOCl₂ or POCl₃.

Needless to say, the protection and deprotection of the amino group ofthe thiazolyl ring are involved in such conventional synthesistechniques for cephalosporin antibiotics.

Besides protection and deprotection of the amino function, the resultingacid chloride, e.g., 2-(2-aminothiazol-4-yl)-2-methoxyimino acetylchloride, 1H-tetrazol-1-acetyl chloride, is unstable, creating furthercomplication for the synthesis of the desired cephalosporin antibiotics.

U.S. Pat. No. 3,954,745 utilizes the same concept, i.e., formation of1H-tetrazol-1-acetyl chloride in dimethylacetamide and coupling the acidchloride with the DMF-solvate of the hydrochloride of7-aminocephalosporin of the following formula VI as shown below to yieldcefazolin. ##STR11##

However, yields are low. Also, the acylating agent, 1H-tetrazol-1-acetylchloride, because of its inherent instability, is difficult to isolateand store at room temperature. Another limitation of this process isthat acylation is to be carried out in strictly anhydrous conditions.

U.S. Pat. No. 5,317,099 describes a process for the synthesis ofβ-lactam derivatives such as cefotaxime and ceftriaxone in whichsilylated 7-ACA is acylated with acyloxyphosphonium chloride derivativeof 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid, which, inturn, is prepared from triphenyl phosphine (TPP), hexachloroethane orcarbontetrachloride and 2(2-aminothiazol-4-yl)-2-syn-methoxyimino aceticacid. Since triphenyl phosphine (TPP) is used as a reactant, the overallcost of coupling the addendum III to the cephalosporin nucleus becomeshigh.

EP 037,380 describes a process for the synthesis of cephalosporinantibiotics, e.g., cefotaxime and ceftriaxone, which comprises acylationof 7-ACA derivatives with an intermediate of formula VII, ##STR12##

However, the synthesis of the 2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid benzthiazolyl thioester from2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid and bisbenzthiazolyl-(2)!disulfide, involves the use of a costly condensationaid such as triphenyl phosphine (TPP), rendering the whole synthesisvery costly.

U.S. Pat. No. 5,037,988 describes a process for the production ofcephalosporins, in particular, cefotaxime and ceftriaxone, in which anactivated form of an organic acid, i.e.,2-(2-aminothiazol-4-yl)-2-oxyiminoacetylsulfite dialkylformiminiumhalide hydrohalide of the following formula VIII; ##STR13## is coupledwith a 7-aminocephaiosporanic acid derivative. The compound of formulaVIII was prepared by reacting 2-(2-aminothiazol-4-yl)-2-oximino aceticacid with dimethyl formiminium chloride chlorosulfite of formula IX,which in turn was prepared by reacting approximately equimolarquantities of thionyl chloride and dimethylformamide at room temperaturein specific solvents only like benzene or toluene, and hence suffersfrom a limitation.

However, poor results have been obtained when an attempt was made toprepare the compound of formula IX in solvents such as chloroform anddichloromethane. In these solvents, the compound IX did not separate outin its characteristic form of insoluble oil, as the polarity of thesesolvents does not allow the formation of these reactants.

Thus, it is evident that the procedures described in the prior art forthe preparation of 7-acylamino cephalosporanic acid derivatives areeither complex, involving protection or deprotection, or costly, or haveother limitations.

SUMMARY OF THE INVENTION

It is thus the primary objective of the present invention to providereactive derivatives of general formula 1 which would be suitable foruse in the manufacture of cephalosporin antibiotics and would not besubject to the above complexities in the manufacture of cephalosporinantibiotics.

Another object of the present invention is directed to provide a processfor the synthesis of the reactive derivatives of2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid(III) and1H-tetrazol-1-acetic acid(IV) of general formula I, which would besimple to manufacture.

Yet a further objective of the present invention is to provide a processfor the synthesis of cephalosporin antibiotics such as cefotaxime,ceftriaxone and cefazolin, which would avoid the protection anddeprotection of the amino group of the thiazolyl ring reported in theknown art.

Another further object of the present invention is to provide a processfor the synthesis of cephalosporin antibiotics of the type mentionedabove which would be simple to carry out and will be cost-effective.

Yet another further object of the present invention is to provide forthe synthesis of cephalosporin antibiotics of the type mentioned abovewhich would favor better and consistent yield of cephalosporinantibiotics with desired characteristics for use as an antibiotic.

Thus, according to one aspect of the present invention, compounds offormula I are produced by a process comprising reacting dimethylformiminium chloride chlorosulphate (DFCCS) of formula XI with2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid(III) or1H-tetrazol-1-acetic acid(IV) in a solvent such as dichloromethane at atemperature ranging from -30° C. to 15° C. to yield the compound offormula I.

In the instance in formula I R₃ = ##STR14## the above reactivederivative of formula I is a reactive derivative of2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid of formula Ia,##STR15## Further, in the instance in formula I, R₃ = ##STR16## theabove reactive derivative of formula I is a reactive derivative of1H-tetrazol-1-acetic acid of formula Ib, ##STR17## In accordance with afurther aspect of the invention, there is provided a process for thepreparation of the desired cephalosporin antibiotics which comprisesreacting silylated 7-aminocephalosporanic acid derivatives of formula X,##STR18## in which R₁ =carboxylic protecting group or hydrogen

R₂ =acetoxy,

R₄ =silyl group or hydrogen

with a reactive derivative of 2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid of formula Ia or 1H-tetrazol-1-acetic acid of formula Ib, indichloromethane at a temperature ranging from -70° C. to -50° C.

Detailed Description of the Invention

Thus, in accordance with the invention, compounds of formula Ia and Ibare prepared by reacting N, N-dimethyl formiminium chloridechlorosulphate (DFCCS) of formula XI, with2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid (III) orIH-tetrazol-1-acetic acid (IV). ##STR19##

DFCCS(XI) is a known compound and described in the literature viz Z.Chem, 6(4), 148 (1966), J. C. S. Perkin Trans I, 2004-2007 (1972); BullChem Soc Jpn, 58, 1063-1064; Adv. Org. Chem. 9(2), 5, (1979); SyntheticReagents Vol. 4, 388-389; Angew Chem Internal Edit, 1(12), 647 (1962).

While DFCCS(XI) prepared by any known process might be used, theinventors have found that best results are obtained when DFCCS(XI) isprepared by the following process.

The preferred process of obtaining the DFCCS(XI) comprises addingsulfuryl chloride to dimethylformamide at -20° C. The temperature israised to 0° C. at which the solid adduct crystallized out, which isvigorously stirred for one hour, followed by addition of dichloromethaneto the resulting reaction mixture. The temperature was raised to 15°C.-20° C. and at this temperature the solid crystals melt, resulting inthe formation of an immiscible layer of the desired adduct, i.e., XI.

Such mode of preparation of DFCCS(XI) is illustrated in the followingscheme A: ##STR20##

The DFCCS(XI) adduct thus obtained by the preferred process of theinvention is found to be advantageous in use in the process ofmanufacture of the reactive derivatives of formula X in accordance withthe objective of the invention for the reasons given below.

i) Unlike the complex IX used in the prior art, DFCCS(XI) used in theprocess of the present invention remains stable and does not getconverted to the normal Vilsmeier's reagent. It has been observed thatDFCCS(XI) of the present invention is apparently more stable thanDFCS(IX) described in U.S. Pat. No. 5,037,988. In particular, it isfound that the thus obtained DFCCS (XI) used in the process of theinvention is distinct from thionyl chloride-DMF adduct, i.e.,dimethylformiminium chloride chlorosulfite(IX) known in the art. Themelting point of the latter is 138°-140° C. Helv. Chim Acta, 62, 1655(1959)! while that of the DFCCS adduct(XI) is 40° C.-41° C. Z. Chem6(4), 148(1966)!.

ii) The DFCCS(XI) used in the process of the invention can be preparedin any solvent such as benzene, toluene, acetonitrile ordichloromethane, and preferably in the absence of solvents. This isadvantageous and clearly distinct from the thionyl chloride--DMF adduct,i.e., dimethylformiminium chloride chlorosulfite described in U.S. Pat.No. 5,037,988, which cannot be prepared in solvents such as chloroformor dichloromethane, since these solvents facilitate complete or partialconversion of dim ethyl formiminium chloride chlorosulfite to normalVilsmeier's reagent.

iii) It has been found that sulfuryl/DMF adduct DFCCS of formula XI ismore stable than DFCS adduct of formula IX made from thionyl chlorideand DMF. Thus, when DFCCS(XI) adduct was kept at ambient temperature for16 hours and used for further complexation with compounds of formula IIIand IV for synthesis of the activated ester required for the finalacylation reaction, the drop in yield in the final antibiotic was about26% (85% when used fresh and 59% after storage of DFCCS for 16 hours).Similarly, when DFCS adduct was kept at ambient temperature for 16 hoursand further processed for synthesis of the final antibiotic, the drop inyield was about 35% (80% when used fresh and 45% when used after 16hours). Hence, DFCCS adduct of formula XI obtained by the preferredprocess described above has superior stability compared to DFCS adductof formula IX and this is a great advantage for cost-effectivemanufacture of cephalosporin antibiotic like Cefotaxime, Ceftriaxone andCefazolin.

Thus, the use of DFCCS(XI) for synthesis of the compound of formula Iaor Ib, the activated ester of compounds of formula III and IV, providesa practical, cost-effective and safe method for manufacture of thedesired cephalosporin antibiotics like cefotaxime, ceftriaxone andcefazolin.

The process of manufacture of the desired cephalosporin antibioticaccording to the improved process of the invention basically involvesthe following:

In Step I, the 2-(2-aminothiazol-4-yl)-2-synmethoxyimino aceticacid(III) was activated with N,N-dimethylformiminium chloridechlorosulphate(XI) in dichloromethane at a temperature ranging from -30°C. to -15° C. to yield reactive form Ia.

In Step II, the reactive form Ia was treated with silylated7-aminocephalosporanic acid (X) at a temperature ranging from -70° C. to-30° C., preferably -55° C., to yield the desired cephalosporins such ascefotaxime, ceftriaxone.

The use of conventional silylating agents such as hexamethyldisilazane,trimethylchlorosilane, bis (trimethyl) silylacetamide is considered tobe appropriate for silylation of 7-ACA. Alternatively,7-amino-cephalosporanic acid can also be used in the form of itsquaternary salt with tetramethyl guanidine.

The basic compounds used as acid scavenging agent to capture HClreleased during silylation include N,N-dimethylaniline, diethylamine,pyridine, preferably N,N-dimethylaniline.

The process of the present invention described above may be representedin scheme B: ##STR21## Cefazolin is prepared from7-amino-3-(2-methyl-1,3,4-thiadiazol-5-yl)thiomethyl-3-cephem-4-carboxylicacid and reactive derivative of 1H-tetrazol-1-acetic acid of formula Ibin a manner similar to that described for the preparation of cefotaxime,ceftriaxone.

The preparation of cefazolin is illustrated in the following scheme C:##STR22## The process of the invention, its objects and advantages willbe further apparent from the non limiting examples illustratedhereunder.

EXAMPLES Example 1 Preparation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid (cefotaxime).

A) Activation of the 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino aceticacid.

11.9 g of sulfuryl chloride was added dropwise to 6.4 g ofdimethlyformamide at -20° C. The temperature was slowly raised to 0° C.at which the solid adduct crystallized out. This was stirred vigorouslyfor 1 hour and 50 ml of dichloromethane was added to the solid crystals.The temperature was raised to 15°-20° C. and at this temperature thecrystallized adduct melted and formed an immiscible layer withdichloromethane. The lower portion (N,N-dimethyl forminium chloridechlorosulphate) was added to a pre cooled slurry of 16.02 g of2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid in 150 ml ofdichloromethane at -20° C. to get a clear solution, which was kept for 1hour at this temperature.

B) Preparation of 7-amino cephalosporanic acid solution.

20.0 g of 7-aminocephalosporanic acid was taken in 150 ml ofdichloromethane and 12.42 g of hexamethyldisilazane was added to it,followed by refluxing for two hours. The clear solution obtained wascooled to 10° C. and 12.1 ml of dimethylaniline was added to it,followed by cooling to -55° C.

C) Acylation

The reaction mixture (A) was cooled to -55° C. and the reaction mixture(B) was added to it to get a clear solution. The temperature wasmaintained at -55° C. for 10 minutes. The quantification of thecondensed mass showed the formation of 82.5% of cefotaxime acid. PMR(DMSO-d₆) δ ppm: 2.00(s), 3.3(q) 3.8(s), 4.9(q) 4.97(q) 5.60(2d),6.70(s), 7.2(bs), 9.47(d).

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid.

200 ml of water was added to the above condensed mass and thetemperature was brought to 25° C. in 20 minutes. At this temperature,the pH of the hydrolyzed mass was brought to 6.5 by using triethylamine.The aqueous layer was taken and 40 ml of 85% formic acid was added at30° C. The product in the formic acid solvate form started precipitatingafter 10 minutes. This was cooled to 5° C. and was stirred for one hourand then filtered to yield 29 g (87%) of the formic acid solvate with apurity of 92%. UV max=233.0 nm (in water)

E) Conversion of formic acid solvate to isopropyl alcohol solvate ofcefotaxime

The above formic acid solvate was taken in 175 ml of isopropyl alcoholand heated to 50° C. for 4-5 hours. The isopropyl alcohol solvate thusformed was cooled to 5° C. and then filtered to yield 26.97 g (81%) ofthe isopropyl alcohol solvate with a purity of 92%. MP=202°-205° C.

a) IR: (main bands) in cm⁻¹. 3420 (--NH₂), 3340 (--NH, --NH₂), 1760(--C═O lactam), 1730 (--C═C, carboxylic, 1650 (--C(═O--NH), 1385-1355(--O--CO--CH₃).

b) UV Characteristics: UV max=235.5 nm (in water), E(1%, 1 cm)=376.00

c) Specific rotation: α!²⁰ _(D) =+61.232 (C=1% aqueous solution)

F) Conversion of Isopropyl alcohol solvate of cefotaxime to cefotaximesodium

10.0 g of the above solvate was taken in 60 ml of methanol and 11 ml ofwater and the mixture was cooled to +5° C. To this was slowly added 1.8g of sodium acetate dissolved in 20 ml methanol to get a clear solution.To the above solution 400 ml of isopropyl alcohol was added within onehour to get cefotaxime sodium in the crystal form.

Example 2 Preparation of7- (2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanic acid (cefotaxime).

Same procedure as in example 1 was followed, but 400 ml ofdichloromethane was used for the activation of2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid. Cefotaxime wasprepared in 81.4% yield.

Example 3 Preparation of 7- (2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanic acid (cefotaxime).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid

Same procedure as in example 1 was followed.

B) Preparation of 7-aminocephalosporanic acid solution

Same procedure as in example 1 was followed.

C) Acylation

The reaction mixture (A) was cooled to -70° C. and reaction mixture (B)was added to it to get a clear solution. The temperature of thecondensed mass was maintained at -70° C. for 10-15 minutes. Thequantification of the condensed mass showed the formation of 75.5% ofcefotaxime.

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid

Same procedure as in example 1 was followed.

Example 4 Preparation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid (cefotaxime)

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid.

19.8 g of sulfuryl chloride was added dropwise to 10.7 g ofdimethylformamide at -20° C. The temperature was slowly raised to 0° C.at which white solid crystallizes out. The reaction mixture was stirredvigorously for one hour. 60 ml of dichloromethane was added to the solidcrystals and the temperature was brought to 15°-30° C. At thistemperature, the solid crystals melted to form immiscible layer. Thelower layer was added to a pre-cooled slurry of 15.08 g of2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid in 120 ml ofdichloromethane at -20° C. to get a clear solution which was kept forone hour at this temperature.

B) Preparation of 7-aminocephalosporanic acid solution

Same procedure as in example 1 was followed.

C) Acylation

The reaction mixture A was cooled to -55° C. and the reaction mixture Bwas added to it to get a clear solution. The temperature was maintainedat -50° C. for 10 minutes. The quantification of the condensed massshowed only 36.3 % of cefotaxime.

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid

Same procedure as in example 1 was followed.

Example 5 Preparation of 7-(2-(2-aminothiazol-4-yl(-2-syn-methoxyimino)acetamido! cephalosporanicacid (cefotaxime)

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid

10.9 g of sulfuryl chloride was added dropwise to 5.9 g ofdimethylformamide at -20° C. The temperature was slowly increased to 0°C. at which the solid adduct crystallized out. This was vigorouslystirred for one hour at this temperature. To the solid crystals, 30 mlof dichloromethane was added and the temperature was raised to 15°-20°C. At this temperature the solid crystals melted and formed animmiscible layer with dichloromethane. The lower layer was added topre-cooled slurry of 15.08 g of2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid in 120 ml ofdichloromethane at -20° C. to get a clear solution which was kept forone hour at the same temperature.

B) Preparation of 7-amino cephalosporanic acid solution

Same procedure as in example 1 was followed.

C) Acylation

The reaction mixture A was cooled to -55° C. and reaction mixture B wasadded to it to get a clear solution. The temperature of the condensedmass was kept at -50° C. for 10 minutes. The quantification of thecondensed mass showed 60% of cefotaxime.

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido!cephalosporanicacid

Same procedure as in example 1 was followed.

Example 6 Preparation of7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido!cephalosporanicacid (cefotaxime).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetic acid.

Same procedure as in example 1 was followed.

B) Preparation of 7-amino cephalosporanic acid solution

Same procedure as in example 1 was followed.

C) Acylation

The reaction mixture A was cooled to -55° C. and the reaction mixture Bwas added to it to get a clear solution. The temperature was maintainedat -50° C. for 30 minutes instead of 10 minutes. The quantification ofthe condensed mass showed 55% of cefotaxime.

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido!cephalosporanicacid

Same procedure as in example 1 was followed.

Example 7 Preparation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid (Cefotaxime).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid.

Same procedure as in example 1 was followed.

B) Preparation of 7-aminocephalosporanic acid solution

20.0 g of 7-aminocephalosporanic acid was taken in 150 ml ofdichloromethane and 12.24 g of hexamethyldisilazane was added to itfollowed by refluxing for 2 hours. The clear solution obtained wascooled to 10° C. and 9.4 g of acetamide was added to it followed bycooling to -55° C.

C) Acylation

Same procedure as in example 1 was followed. Quantification of thecondensed mass showed 60% of cefotaxime.

D) Isolation of 7-(2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido! cephalosporanicacid

Same procedure as in example 1 was followed.

Example 8 Preparation of 7- (2-(2-aminothiazol-4-yl)-2-syn-methoxyiminoacetamido) cephalosporanic acid (cefotaxime).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid.

11.9 g of sulfuryl chloride was added dropwise to 6.4 g ofdimethylformamide at -20° C. The temperature was slowly raised to 0° C.at which the solid adduct crystallizes out. This was stirred vigorouslyfor one hour and 50 ml of dichloromethane was added to the solidcrystals. The temperature was raised to 15°-20° C. and at thistemperature, the crystallized adduct melts and forms an immiscible layerwith dichloromethane. The lower portion (N,N-dimethyl forminium chloridechloro sulphate) was added to a pre-cooled slurry of 16.25 g of2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid in 150 ml ofdichloromethane at -20° C. to get a clear solution, which was kept forone hour at this temperature.

B) Preparation of 7-amino cephalosporanic acid solution

20.0 g of 7-amino cephalosporanic acid was taken in 120 ml of CH₂ Cl₂and 10.65 gm hexamethyl disilazane and 0.1 gm imidazole was added to it.Start refluxing for 4.0 hours under N₂ atmosphere. (After 30 minutes torefluxing, clear solution obtained.) Cooled to 10° C. and 12.1 mldimethyl aniline was added followed by cooling to 55° C.

C) Acylation

The reaction mixture A was cooled to -55° C. and the reaction mixture Bwas added to it to get a clear solution. The temperature was maintainedat -55° C. for 10 minutes. The quantification of the condensed massshowed the formation of 90-95% of cefotaxime acid depending on thepotency of the starting product (7-ACA).

D) Isolation of7-((2-(2-aminothiazol-4-yl)-2-syn-methoxyimino)acetamido!cephalosporanicacid

80 ml of water was added to the above condensed mass and the temperaturewas brought to 25° C. in 20 minutes. At this temperature, the pH of thehydrolyzed mass was brought to 6.5 by using triethylamine. The aqueouslayer separated. Organic layer was extracted with 20×2 ml DM Water.Combined aqueous layer and extraction was taken and 40 ml of 85% formicacid was added at 30° C. The product in the formic acid solvate formstarts precipitating after 10 minutes. This was cooled to 0°-5° C. andwas stirred for one hour and then filtered to yield 30 gm (87%) of theformic acid solvate with a purity of 92%.

E) Conversion of formic acid solvate to isopropyl alcohol solvate ofcefotaxime

Same procedure as in example 1 was followed.

F) Conversion of isopropyl alcohol solvate of cefotaxime to cefotaximesodium.

Same procedure as in example 1 was followed.

Example 9 Preparation of 7-(1-(1H)-tetrazolylacetamido)-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acid(Cefazolin).

A) Activation of 1H-tetrazol-1-acetic acid

9.41 g of sulfuryl chloride was added dropwise to 5.09 g ofdimethylformamide at -20° C. The temperature was slowly raised to 0° C.at which the solid adduct crystallized out. To this 50 ml ofdichloromethane was added and the solid crystals melted to form animmiscible layer. The lower layer was added to 8.9 g of1H-tetrazol-1-acetic acid in 120 ml of dichloromethane at -20° C. Thetemperature was raised to 0° C. which resulted in the formation of aturbid reaction mass. This reaction mass was kept at 0° C. for one hour.

B) Preparation of 7-amino-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acidsolution

20.0 g of 7-amino-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acidwas taken in 120 ml dichloromethane and to this 9.39 g of hexamethyldisilazane was added and refluxed for two hours to get a clear solution.After two hours, the clear solution was cooled to 10° C. and 12.6 gdimethylaniline was added to it and the reaction mixture was furthercooled to -40° C.

C) Acylation

The reaction mixture A was cooled to -40° C., to which reaction mixtureB was added and the temperature of the condensed mass was maintained at-25° C. for 10-15 minutes. The quantification of condensed mass showed53% of cefazolin. PMR(DMSO-d₆) δ ppm: 2.7(s,3H), 3.7(dd,2H),4.35(dd,2H), 5.15 (d,1H), 5.4(s,2H), 5.8(q,1H), 9.39(s,1H), 9.6(d,2H).

D) Isolation of 7-(1-(1H)-tetrazolylacetamido)-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acid.

To the above condensed mass, 100 ml of water was added and the pH wasbrought to 6 by using triethylamine. The layer was separated and the pHof the aqueous layer was adjusted to 1.5 to yield white crystals ofcefazolin. This was filtered and washed with water, followed bymethanol.

a) IR: (Main bands) in cm⁻¹ 3280 (--NH), 3140, 3075 (N═N, --C═N--tetrazole ring), 2620, 2580 (--OH, bonded, --COOH), 1770 (C═O lactam),1715 (C═O acid), 1670 (C═O amide-I), 1555 (C═O amide-II).

b) UV Characteristics: UV max=272.5 nm (in water), E(1%, 1 cm)=290.76

c) Specific Rotation: a!²⁰ _(D) =-19.6 (C=1% aqueous solution)

Example 10 Preparation of 7-(1-(1H)-tetrazolylacetamido)-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acid

A) Activation of 1H-tetrazol-1-acetic acid.

Same procedure as in example 8 was followed. But 140 ml ofdichloromethane was used for activation.

B) Preparation of 7-amino-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acidsolution

20.0 g of7-amino-3-(2-methyl-1,3,4-thiadiazol-5-yl)thiomethyl-3-cephem-4-carboxylicacid was taken in 140 ml dichloromethane and hexamethyldisilazane wasadded and refluxed for two hours to get a clear solution. This solutionwas cooled to 10° C. and 12.6 g of dimethylaniline was added. Theresulting mixture was cooled to -40° C.

C) Acylation

The reaction mixture A was cooled to -40° C. to which reaction mixture Bwas added and the temperature of the resulting condensed mass wasmaintained at -25° C. for 10-15 minutes. The quantification of thecondensed mass showed 61% of cefazolin.

D) Isolation of 7-(1-(1H)-tetrazolylacetamido)-3-2-(5-methyl-1,3,4-thiadiazolyl)thiomethyl!-3-cephem-4-carboxylic acid.

Same procedure as in example 9 was followed.

Example 11 Preparation of7-(((2-aminothiazol-4-yl)(methoxyimino)acetyl)amino)-8-oxo-3-(((1,2,5,6-tetrahydro-2-methyl-5,6-dioxo-1,2,4-triazin-3-yl)thio)methyl)-5-thia-1-azabicyclo(4.2.0)oct-2-ene-carboxylic acid)ceftriaxone)

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid

9.06 g of sulfuryl chloride was slowly added to 4.91 g ofdimethylformamide at -25° C. The temperature was slowly raised to 0° C.in 60-90 minutes. At this temperature, white solid, i.e., dimethylforminium chloride chlorosulfate (DFCCS), crystallizes out, 50 ml ofdichloromethane was added to the solid crystals and stirred vigorouslyfor 15-20 minutes when the solid crystals melt to form an immisciblewhite crystalline colored oil. The immiscible oil was decanted in thelower portion and was slowly added to 11.37 g of 2-(2-aminothiazol-4-yl)methoxyimino acetic acid in 120 ml of dichloromethane cooled to -30° C.in 20-30 minutes. The temperature was slowly raised to -10° C. in onehour to get a clear solution.

B)7-amino-3-desacetoxy-3-((2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio) cephalosporanic acid solution

20.0 g of7-amino-3-desacetoxy-3-((2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio)cephalosporanic acid in 160 ml of dichloromethane. To the resultingreaction mixture 40 mi of N,O-bis-silyl acetamide was added and stirredfor eight hours at 30° C. to get a clear solution, cooled at -20° C. and8.35 ml dimethylaniline was added to it and the reaction mixture wasfinally cooled to -50° C.

C) Acylation

The reaction mixture A was cooled to -30° C. and added to the reactionmixture B. The temperature was maintained at -40° C. for 20-30 minutes.

Thick precipitation occurred which became thin during stirring, HPLCshowed the formation of 70% of ceftriaxone.

PMR (DMSO-d₆) δ ppm: 3.3(d), 3.59(s), 3.9(s), 4.2(d), 5.1(d), 5.72(d),6.8(s), 9.7(d).

D) Isolation

After 30 minutes of the reaction, 200 ml of water was added at -40° C.and stirred for 30 minutes at 20°-25° C. The pH of the reaction mass wasbrought to 6.5 by adding triethylamine. The aqueous layer was separatedand was treated with 5.0 g of activated carbon and 2.0 g of sodiumbisulfate for 30 minutes, filtered and washed with 40 ml of water. ThepH is then adjusted to 3.2 by 1:1 HCl, seeded and the resulting mixturewas stirred for 30 minutes and then further stirred for two hours at 0°C. to -5° C. The product was filtered, washed with chilled isopropylalcohol to give 21 g (70%) of Ceftriaxone, Assay=92.88%-95%.

Example 12 Preparation of 7-(2-aminothiazol-4-yl)-2-syn-methoxyimino!acetamido!-8-oxo-3-(1,2,5,6-tetrahydro-2-methyl-5,6-dioxo(-1,2,4 triazin-3-yl)thiomethylcephalosporamic acid(ceftriaxone).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid.

Same procedure as in example 11 was followed.

B) Quaternary salt of7-amino-3-desacetoxy-3-(2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio)cephalosporin acid.

20.0 g of7-amino-3-desacetoxy-3-(2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio)cephalosporanicacid in 120 ml of dichloromethane was cooled to -15° C. and 12.3 g oftetramethyl guanidine (TMG) was added to it. The temperature was slowlyraised to -20° C. to -25° C. in one hour. The reaction mixture wasstirred for one hour at 25° C. to get a clear solution. This solutionwas further cooled to -30° C. to -35° C. and 8.35 ml dimethylaniline wasadded to it and the reaction mixture was finally cooled to -40° C.

C) Acylation

Same procedure as in example 11 was followed. HPLC showed formation of75% of ceftriaxone.

D) Isolation

Same procedure as in example 11 was followed.

Example 13 Preparation of 7-(2-aminothiazol-4-yl)(methoxyimino)acetamido!-8-oxo-3-(1,2,5,6-tetrahydro-2-methyl-5,6-dioxo 1,2,4-triazin-3-yl)thio!methyl!cephalosporanic acid (ceftriaxone).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid.

Same procedure as in example 11 was followed.

B) 7-amino-3-desacetoxy-3-(2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio!cephalosporanicacid solution.

20.0 g of7-amino-3-desacetoxy-3-(2,5-dihydro-6-hydroxy-2-methyl-5-oxo-as-triazin-3-yl)thio)cephalosporanicacid in 200 ml of dichloromethane was taken and 19.05 g oftrimethylsilyl chloride (TMCS) was added to it, followed by refluxingfor three hours to give clear solution, cooled to -20° C. and 8.53 mldimethylamine was added to it. The reaction mixture was finally cooledto -50° C.

C) Acylation

Same procedure as in example 11 was followed. HPLC showed conversion to70% of ceftriaxone.

Example 14 Preparation of7-(((2-aminothiazol-4-yl)(methoxyimino)acetyl)amino)-8-oxo-3-(((1,2,5,6-tetrahydro-2-methyl-5,6-dioxo-1,2,4-triazin-3-yl)thiomethyl)-5-thia-1-azabicyclo(4.2.0) oct-2-ene-2-carboxylic acid (Ceftriaxone).

A) Activation of 2-(2-aminothiazol-4-yl)-2-syn-methoxyimino acetic acid

8.72 g of sulfuryl chloride was slowly added to 4.7 g of dimethylformamide at -25° C. The temperature was raised slowly to 0° C. in 60-90minutes. Dimethyl forminium chloride chlorosulphate (DFCCS) crystallizesout at 0° C. 50 ml of dichloromethane was added to the solid crystals,which melts to get a colorless insoluble oil. This oil was decanted andtaken separately. 11.37 g of2-(2-aminothiazol-4-yl) methoxyimino aceticacid was taken in 120 ml dichlomethane and cooled to -30° C., to whichthe above-said oil is added. The temperature was slowly raised to -10°C. to get a clear solution and was kept at this temperature for 30minutes.

B) Preparation of7-amino-3-desacetoxy-3-((2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-yl)thio)cephalosporanic acid solution

20.0 g of dry7-amino-3-desacetoxy-3-(2,5-dihydro-6-hydroxy-3-methyl-5-oxo-as-triazin-3-ylthio) cephalosporanic acid was taken in 120 ml of dichloromethane towhich 13.05 g of hexamethyldisilazane, 2.5 g of trimethyl chlorosilaneand 0.5 g of imidazole were added and refluxed for 5-6 hours to get ahazy reaction mixture. This was cooled to 10° C. and 8.3 ml ofN,N-dimethyl aniline was added and was further cooled to -50° C.

C) Acylation

Reaction mixture A was cooled to -50° C. and reaction mixture B wasadded to A to get a clear solution and the resulting temperature of thereaction mixture was maintained at -45° to -50° C. for 30 minutes. HPLCmonitoring showed the formation of ceftriaxone 86%.

D) Isolation

After 30 minutes, 200 ml of water and 50 ml of triethylamine was addedto get pH 6.5-7.0. The layer was separated and the aqueous layer wastaken and 20 ml of isopropyl alcohol and 40 ml of ethyl acetate wasadded and stirred for 10 minutes at 20°-25° C. pH of this aqueous layerwas adjusted to 2.5 by using formic acid to get white crystals. This wasfurther cooled to 0°-5° C. and maintained for one hour. After one hour,the product was filtered and washed with 50 ml of chilled water. Theproduct was dried under vacuum to get white crystals of purity 98%.

We claim:
 1. A process for producing a compound of formula I ##STR23##wherein R₃ = ##STR24## the process comprising; reacting dimethylformiminium chloride chloro sulphate of formula XI ##STR25## with2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid or1H-tetrazol-1-acetic acid in a solvent at a temperature ranging from-30° C. to -15° C.
 2. A process as claimed in claim 1, wherein thetemperature is about -20° C.
 3. A process as claimed in claim 1, whereinthe solvent is selected from the group consisting of dichloromethane,chloroform, benzene, and toluene.
 4. A process as claimed in claim 1,wherein the dimethyl formiminium chloride chloro sulphate of the formulaXI is obtained by reacting dimethyl formamide with sulfuryl chloride,and the compound of formula I is a reactive derivative of the formula Iaobtained by reacting the 2-(2-aminothiazol-4-yl)-2-methoxyimino aceticacid with the dimethyl formiminium chloride chloro sulphate of formulaXI ##STR26## or is a reactive derivative of formula I(b), obtained byreacting the 1H-tetrazol-1-acetic acid with the dimethyl formiminiumchloride chloro sulphate of formula XI ##STR27##
 5. A process as claimedin claim 4, wherein the molar ratio of the dimethyl formiminium chloridechloro sulphate with respect to the2-(2-aminothiazol-4-yl)-2-methoxyimino acetic acid or the1H-tetrazol-1-acetic acid is in the range of 1.1-1.2:1.
 6. A process asclaimed in claim 5, wherein the molar ratio is 1.17:1.